This proposal examines the hypothesis that diabetes results in a pathological change in the communication between the bone marrow (BM) and gut leading to dysfunction in both compartments. Angiotensin converting enzyme 2 (ACE2) converts angiotensin II (ANG II) to angiotensin 1-7(Ang 1-7) which, by virtue of its actions on the Mas receptor, opposes the molecular and cellular effects of ANG II. In human subjects with diabetes, sustained activation of the ACE2/Ang 1-7/Mas axis in a key BM population (CD34+ cells) was associated with protection from development of diabetic retinopathy. Ace2/Ace1 mRNA ratio was reduced in small intestine epithelial cells (IEC) and in BM cells of diabetic mice and these changes are associated with both gut and BM pathology. Microbiota studies comparing Akita mice and Ace2- /- Akita mice demonstrate that the loss of ACE2 results in significant phylogenetic differences and these changes are associated with increased infiltration of proinflammatory BM cells into the gut. These novel findings have led us to propose the following hypothesis: Dysregulated RAS resulting in reduced ACE2 in BM and gut drives the disturbed BM-gut axis in diabetes. Increasing ACE2 expression in BM or IEC, either by genetic or pharmacological manipulations, will restore reciprocal communication between BM and gut preventing development of diabetic retinopathy. Aim 1: In Akita mice, to determine whether increasing ACE2 expression in hematopoietic cells will facilitate maintenance of endothelial and epithelial barrier functions in retina and gut. Hematopoietic-specific Ace2 transgenic mice (Vav1-CreAce2KI) will be crossed with Akita mice to generate Vav1-CreAce2KI.Akita mice (Model 1). Vav1-CreAce2KI will provide donor BM for BM transplantation into Akita mice (Model 2). Aim 2: To determine whether sustained ACE2 expression in hematopoietic cells will prevent diabetes-induced dysbiosis and development of DR. Aim 3. To determine whether correction of dysbiosis by exogenous administration of genetically modified probiotics expressing ACE2 or overexpression of ACE2 in intestinal epithelial cells of the gut will protect from development of DR.